High Temperature Imaging Media for Digital Image Correlation

ABSTRACT

A thermal barrier coating is provided. The thermal barrier coating is configured to remain adherent to the substrate under high strains, thus allowing the use of non-contacting strain measurement systems, such as digital image correlation. The thermal barrier coating may include a first layer of a partially metallic material configured to adhere to a metallic substrate, and a second layer of a partially ceramic material configured to adhere to the first layer. A successful configuration has a top layer thickness that is approximately two-thirds of the first layer thickness.

CROSS-REFERENCE TO RELATED APPLICANT

This is a non-provisional US patent application claiming priority underU.S.C §119(e) to U.S. Provisional Ser. No. 61/900,752 filed on Nov. 6,2013

FIELD OF THE DISCLOSURE

The present disclosure generally relates to thermal barrier coatings,and particularly to thermal barrier coatings for use in non-contactcharacterization of high temperature materials.

BACKGROUND OF THE DISCLOSURE

Thermal barrier coatings are applied to a variety of materials typicallyexposed to high temperatures or high temperature gradients. Thermalbarrier coatings are typically applied to the surfaces of metallicsubstrates to insulate and protect the general integrity of theunderlying substrate from prolonged thermal loads. The uniquecharacteristics of thermal barrier coatings allow for expanded use innon-contact strain measurements.

Conventional thermal barrier coatings are comprised of two or morelayers, such as a bond coat, a thermally grown oxide and a top layer.The bond coat is typically formed of a metallic material or metal alloywhich provides an adhering interface between the top coat and thesubstrate. Existing non-contact strain measurements are limited torelatively low temperatures (<1000° F.), and strain levels less than˜10%. These limits are associated with the materials, such as ceramicpaint, used to provide optical contrast.

Ceramic paints are limited both in temperature capability and straincompatibility. They are susceptible to spalling and flaking at highstrain levels. Degradation of this type will preclude successful use ofa non-contact strain measurement technique such as digital imagecorrelation. The present disclosure is directed at addressing one ormore of the deficiencies set forth above.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a thermal barriercoating is provided. The thermal barrier coating includes a bond layerhaving a first thickness, and a top layer having a second thickness thatis approximately two-thirds of the first thickness.

In a refinement, one or more of the bond layer and the top layer may beconfigured to maintain substantial adherence with a metallic substrateat temperatures of at least approximately 1400° F. and under strainlevels of at least approximately 30%.

In accordance with another aspect of the disclosure, a thermal barriercoating is provided. The thermal barrier coating includes a metallicbond coat having a thickness of approximately 0.003 inches, and a secondlayer ceramic top coat having a thickness of approximately 0.002 inches.

In accordance with yet another aspect of the disclosure, a method ofapplying a thermal barrier coating onto a metallic substrate isprovided. The method includes applying a first layer of a partiallymetallic material of a first thickness to a surface of the metallicsubstrate; and applying a second layer of a partially ceramic materialof a second thickness to the first layer. The second layer is appliedsuch that the second thickness is approximately two-thirds of the firstthickness.

These and other aspects of this disclosure will become more readilyapparent upon reading the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged, cross-sectional view of one exemplary thermalbarrier coating constructed in accordance with the teachings of thepresent disclosure;

FIG. 2 is a perspective view of a sample substrate having a thermalbarrier coating applied thereon;

FIG. 3 is a perspective view of the sample substrate of FIG. 2 with athermal barrier coating thereon at 1400° F. after 10% strain;

FIG. 4 is a perspective view of the sample substrate of FIG. 2 with athermal barrier coating thereon at 1400° F. after 20% strain; and

FIG. 5 is a perspective view of the sample substrate of FIG. 2 with athermal barrier coating thereon at 1400° F. after 30% strain.

While the present disclosure is susceptible to various modifications andalternative constructions, certain illustrative embodiments thereof havebeen shown in the drawings and will be described below in detail. Itshould be understood, however, that there is no intention to be limitedto the specific forms disclosed, but on the contrary, the intention isto cover all modifications, alternative constructions, and equivalentsfalling with the spirit and scope of the present disclosure.

DETAILED DESCRIPTION

Referring to FIG. 1, one exemplary embodiment of a thermal barriercoating 20 which may be applied to a metallic substrate 22 is provided.As shown, the thermal bather coating 20 may include a plurality oflayers configured to bond against one another as well as with a givensurface of the metallic substrate 22 in a manner which substantiallywithstands relatively high temperatures, for example, approximately1400F or greater, and relatively high strain levels, for example, strainlevels of approximately 30% or greater. More particularly, the thermalbarrier coating 20 may be structured to substantially maintain theintegrity thereof and thereby enable non-contact characterization of themetallic substrate 22, such as by digital image correlation, or thelike, under both high temperature and high strain conditions.

As shown in FIG. 1, the thermal barrier coating 20 may include a firstcoat or layer 24 that is configured to adhere or bond with a surface ofa metallic substrate 22. More specifically, the first layer 24 may beapplied in the form of a bond coat or layer 24 as is commonly used inthe art. The bond layer 24 may be generally metallic, or at leastpartially composed of a metallic substance or material, such as in theform of a metal alloy, or the like. Moreover, the bond layer 24 may becomposed of any material commonly used in the art that is suited toadhere to the metallic substrate 22 and provide a sufficient interfacebetween the metallic substrate 22 and any one or more additional layersof the thermal barrier coating 20. Furthermore, the bond layer 24 may beapplied onto the surface of the metallic substrate 22 in the form of aspray or any other means conventionally used in the art.

The thermal barrier coating 20 of FIG. 1 may additionally include asecond layer 26 that is configured to adhere or bond with the first orbond layer 24. The second layer 26 may be applied, for example, viaspray, or the like, onto the bond layer 24 in the form of a top coat orlayer 26 as is commonly used in the art, and composed of a generallyceramic material. For example, the top layer 26 may include any one ormore of yttria-stabilized zirconia (YSZ), alumina compounds, or anyother material capable of sufficiently adhering with the bond layer 24.

Still referring to FIG. 1, the thermal barrier coating 20 mayadditionally include a third layer or a thermally grown oxide layer 28that is generally disposed between the first layer 24 and the secondlayer 26. In particular, the thermally grown oxide layer 28 may becomposed of a slow-growing oxide that is formed through oxidation of thebond layer 24, which may further serve to generally protect the bondlayer 24.

Furthermore, the bond layer 24 and the top layer 26 of the thermalbarrier coating 20 of FIG. 1 may be provided with different thicknessesto exhibit different properties under high temperatures and high strainlevels. As shown in FIG. 1, for example, the bond layer 24 may beprovided with a thickness of t₁, while the top layer 26 may be providedwith a thickness of t₂. Moreover, the bond layer 24 and the top layer 26may be configured such that the second thickness t₂ is approximatelytwo-thirds of the first thickness t₁. For example, the bond layer 24 mayhave a thickness of approximately 0.003 inches and the top layer 26 mayhave a thickness of approximately 0.002 inches. Such thicknesses of thebond layer 24 and the top layer 26 have been found to exhibit desirableresults under high temperatures (approximately 1400° F. to approximately1600° F. or greater) and high levels of strain (approximately 30% toapproximately 40% or greater).

Turning now to FIGS. 2-5, one exemplary thermal barrier coating 20 isapplied to a sample metallic substrate 22 and tested under hightemperature and high strain conditions. For example, the thermal barriercoating 20 applied may include a bond layer 24 having a thickness ofapproximately 0.003 inches and two passes of a top layer 26 having anoverall thickness of approximately 0.002 inches. As shown, FIG. 2illustrates the substrate 22 as coated with the thermal barrier coating20 as described and prior to being subjected to any high temperatures orhigh strain conditions. Furthermore, FIG. 3 illustrates the thermalbarrier coating 20 at 1400° F. after 10% strain, FIG. 4 illustrates thethermal barrier coating 20 at 1400° F. after 20% strain, and FIG. 5illustrates the thermal barrier coating 20 at 1400° F. after 30% strain.As more clearly shown in FIG. 5, the integrity of the thermal barriercoating 20 may be substantially intact while exhibiting surface cracksunder high temperatures and high levels of strain. Moreover, the networkof surface cracks are desirable as they are indicative of coatingbehavior with the ability to assess or map relatively high levels ofstrain on the sample substrate 22 using non-contact characterizationmeans, such as digital image correlation, or the like, that wasotherwise not possible under such high temperatures due to flaking,spalling, or other modes of degradation.

The foregoing disclosure is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the presentdisclosure may be practiced other than as specifically described. Forthat reason, the appended claims should be studied to determine truescope and content.

What is claimed is:
 1. A thermal barrier coating, comprising: a bondlayer having a first thickness; and a top layer having a secondthickness that is approximately two-thirds of the first thickness. 2.The thermal barrier coating of claim 1, wherein one or more of the bondlayer and the top layer is configured to maintain substantial adherencewith a metallic substrate at temperatures of at least approximately1400° F. and under strain levels of at least approximately 30%.
 3. Thethermal barrier coating of claim 1, wherein the top layer is at leastpartially formed of a ceramic material.
 4. The thermal barrier coatingof claim 1, further comprising a thermally grown oxide layer that isdisposed between the bond layer and the top layer.
 5. A thermal barriercoating, comprising: a first layer of a partially metallic materialconfigured to adhere to a metallic substrate, the first layer having athickness of approximately 0.003 inches; and a second layer of apartially ceramic material configured to adhere to the first layer, thesecond layer having a thickness of approximately 0.002 inches.
 6. Thethermal barrier coating of claim 5, wherein one or more of the firstlayer and the second layer is configured to maintain adherence with themetallic substrate at temperatures of at least approximately 1400° F.and under strain levels of approximately 30% strain.
 7. The thermalbarrier coating of claim 5, wherein one or more interfaces between thefirst layer and the second layer is configured to enable non-contactcharacterization of a sample substrate under high temperature and highstrain conditions.
 8. The thermal barrier coating of claim 5, whereinthe first layer is a bond layer configured to adhere to the metallicsubstrate, and the second layer is a top layer configured to adhere tothe first layer.
 9. The thermal barrier coating of claim 5, furthercomprising a third layer formed of an at least partially oxide material,the third layer being disposed between the first layer and the secondlayer.
 10. The thermal barrier coating of claim 5, wherein each of thefirst layer and the second layer is applied by one or more spray coats.11. A method of applying a thermal barrier coating onto a metallicsubstrate, the method comprising: applying a first layer of a partiallymetallic material of a first thickness to a surface of the metallicsubstrate; and applying a second layer of a partially ceramic materialof a second thickness to the first layer, the second layer being appliedsuch that the second thickness is approximately two-thirds of the firstthickness.
 12. The method of claim 11, wherein one or more of the firstlayer and the second layer is configured to maintain adherence with thesurface of the metallic substrate in temperatures of at leastapproximately 1400° F. and under strain levels of approximately 30%strain.
 13. The method of claim 11, wherein the first layer is a bondlayer and is bonded to the surface of the metallic substrate, and thesecond layer is a top layer and is bonded to the first layer.
 14. Themethod of claim 11, wherein each of the first layer and the second layeris applied by one or more spray coats.